Structures formed by piling, stacking, organizing or confining soils, sands, rocks, aggregates and the like for both temporary and permanent placement are well known. Examples of such structures range from rock riprap and gabions, to sand filled bags, and are constructed and reinforced with a variety of elements formed from concrete, wood, stone, metal or plastic. Geotextile may also be used to support an underlayment, line gabions or for similar operations to retain aggregate that would normally be lost from the structure and thereby minimize the fill required. While known structures and their related shaping and reinforcing elements can be successfully employed, each has various shortcomings and disadvantages.
For example, the large rocks required for riprap, a common solution for water erosion, may not be readily available. If available, structuring the riprap requires special handling equipment and careful placement or else a significant portion of the large rocks ineffectively accumulate at the bottom of the riprap structure making it necessary to use substantially more material than would otherwise be required. When the large rocks required for riprap are not available, gabions filled with smaller rocks or stones may be substituted. However, because their bulk makes transportation uneconomical, gabions are usually constructed on site and such construction, placement and filling of gabions is very expensive, labor intensive and requires some skill for proper construction.
Slope stabilization may also be accomplished by placing bags or mats which are pumped full of concrete or sand and gravel. While concrete is much more permanent, the expense and availability problems are obvious. When sand and gravel are used, tearing and deterioration present hazards. Transverse arrays of beams, of course, can also be used for slope protection, with the beams being tied into the slope at appropriate intervals. With this arrangement, the durability, cost and extensive excavation required may be prohibitive.
Confinement structures formed by pumping concrete, sand or gravel into tubes, bags or the like are suggested by the basic sandbag confinement structure which is used in many applications, e.g., floodwalls, revetments, barriers, embankments, bulwarks and fortifications. Sandbags can be filled by hand or machine. However, machine filling is uncommon, and of course, requires specialized machinery, while hand filling is very labor intensive and time consuming. Here again, structures formed from filled sandbags are susceptible to tearing and deterioration which can lead to localized failure, and ultimately, the failure of the entire structure.
Crushed stone or gravel is used as a load bearing surface or an underlayment for the construction of roads, railroads and runways. Rutting and failure may quickly occur if such an underlayment is placed on a low bearing strength subgrade. To overcome early failure, a geotextile layer may be placed over the subgrade before the stone bed is formed as previously noted. Still, rutting occurs with time. In addition, a substantial depth of stone fill is still required, and such stone fill may be unavailable or difficult and expensive to obtain. To overcome the problems with such subgrades, a honeycomb-like structure made of strips of plastic material has been provided. The strips are welded together at intervals and may be stretched apart to form individual honeycomb cells, with the cells being filled by the crushed stone or gravel to form the underlayment. Such honeycomb structures, though effective, are heavy and awkward to handle, typically requiring two men to carry a collapsed grid and four to expand the grid prior to filling. Such honeycomb grids have also been reported to be fragile in use.
As an alternative to the plastic honeycomb grids previously mentioned, generally rectangular gridworks formed of aluminum strips have been employed as underlayments. In these structures, a series of strips of aluminum are slotted on one side to approximately the center of the strips. A plurality of the strips are then positioned on edge in a grid or network pattern, with strips running in one direction having the slots directed downwardly and engaging corresponding upwardly facing slots of perpendicularly oriented strips to define a rectangular gridwork of rectangular cells for receiving sand, crushed stone or gravel therewithin.
Such prior art aluminum gridworks resemble "eggcrates." The intersections of the individual strips must be secured to one another, for example, by taping, to prevent the strips from falling from the gridwork if the gridwork is moved as a unit. Such gridworks can be collapsed to form a multilayer strip somewhat longer than any strip comprising the gridwork. While the honeycomb and aluminum gridworks have proved moderately effective, they are expensive and difficult to construct and handle. Further, such gridworks cannot be palletized for storage and transport, and where aluminum strips are used in their construction, such gridworks are subject to bending if improperly handled, which bending can impair or destroy their utility.
It is apparent that the need exists for a lightweight inexpensive confinement and reinforcement structure which would have a broad utility in place of many, if not all, of the noted earthwork structures as well as other applications and which is easy to transport and deploy such that it can be filled with locally available sand, soil, rocks or other fluent materials, either manually or by means of readily available general purpose equipment.